Land based military forces use specialized trailers as mobile command posts, communication centers and in-field combat support locations. These trailers may have box-like expansion modules that translate outboard to enlarge interior space of the trailer. Various mechanisms have been used to translate the extension modules. Many such mechanisms have insufficiently straight, level translation paths of the module, whereby elements of the module's roof and floor bind with elements of the trailer's roof and floor.
My expansion linkage provides essentially straight line module translation and thus prevents binding between the module and the trailer. My linkage has two cross arms intersecting to form a scissor-like connection. One is a trailer cross arm that pivots to the trailer and the other is a module cross arm that pivots to the module. The cross arms' pivot axes are at ends of the cross arms, and lie in a line generally parallel to the module's translation path. At opposite ends of the cross arms from their pivot axes are swingable linkage arms. One linkage arm connects the trailer cross arm to the module while the other linkage arm connects the module cross arm to the trailer. The intersection of the cross arms is 2/3 to 3/4 the distance from the cross arms' pivot axes to their connections with the linkage arms.